Well, first of all, a pure electric car will be the absolutely least cost to operate.
No spark plugs, no timing belt, reduced brake wear, minimal fuel charges, not having to spend *time* at the pump, etc, an electric car is great.
But that aside, a hybrid is pretty low maintinence also. I believe that the Prius should actually be less maintinence than a Corolla. Compared to the Corolla, the Prius should have--
-- less wear on transmission
-- Much less wear on brakes
-- not have to worry about timing belt replacement